Could mild painkillers, taken by women during pregnancy, be linked to male fertility problems?
The question is raised by a new study which suggests that these over-the-counter analgesics may be a greater risk than hormone-disrupting chemicals and plastics that are most blamed for causing reproductive problems in later life.
Researchers pored over data from 834 women in Denmark and 1,463 in Finland who were questioned during their pregnancy about their health and use of medication.
They found nothing that was statistically interesting in the Finnish group, but in the Danish group, two startling phenomena emerged.
Women who took a combination of one or more painkiller -- such as aspirin and paracetamol together -- during pregnancy had a seven-fold increased risk of giving birth to sons with undescended testicles.
This condition, known as cryptorchidism, is a risk factor in poor semen quality and a form of testicular cancer in later life.
In addition, those who took any analgesic during the second trimester of pregnancy more than doubled the risk of cryptorchidism for their child.
"We do not quite understand why the Finnish cohort (group) does not show the same associations as the Danish cohort," said Henrik Leffers, senior scientist at Rigshospitalet in Copenhagen, who led the research.
"However, the use of mild analgesics in the Finnish cohort was only examined by questionnaires, not by telephone interviews, and the telephone interviews gave the most reliable information in the Danish cohort, which may explain some of the differences."